Senator Brandis said the museum must be seen to be apolitical, and it was not appropriate for a working political journalist to hold the chairman's role.

He said the circumstances did not reflect on Cassidy personally, and said the broadcaster's decision to stand aside was an "unselfish act".

In a letter to the director of the Museum of Australian Democracy at Old Parliament House, Daryl Karp, Cassidy wrote that he was resigning to prevent damage to the institution.

"I am of the belief that remaining in the position would shroud the board and the institution in ongoing controversy; and that's the last thing that I want," he wrote.

In his resignation letter, Mr Cassidy said Senator Brandis explained that he has "a strong view" that it is not appropriate for journalists or politicians involved in the political process to sit on such boards.

The Abbott Government is entitled to wind back the media focus. But not to the point where routine scrutiny is almost impossible, writes Barrie Cassidy.

Photo: AAP

On Friday morning, Cassidy defended his appointment and told News Breakfast he was approached in June to take over the vacant chairman position.

"It's an honorary position. It comes with no money. You volunteer your services," Cassidy said.

"It was signed off on in August and The Australian put it on page one and sort of said it was all shrouded in secrecy and so on."

Cassidy says he wants to know if other Labor government appointments will be reviewed to establish that there was nothing personal about Senator Brandis's request.

He says he is prepared to accept the Coalition has genuine concern about appointments in the last days of a government, but he wants evidence that it will be consistent.

He has requested that Senator Brandis outline what he knows about other appointments that were made around the same time.

Barrie Cassidy's resignation letter

25.10.2013

To Daryl Karp

Director

Australian Museum of Democracy, Old Parliament House.

Dear Daryl.

I wish to inform you that forthwith I am resigning from the position of chairman of the Advisory Board. I have already informed the Minister of my intentions.

I am of the belief that remaining in the position would shroud the board and the institution in ongoing controversy; and that's the last thing that I want.

The Minister explained to me that he has a high regard for me personally, but nevertheless has (a) concerns about the process leading up to the appointment; and (b) a strong view that it is not appropriate to have anybody currently involved in the political process, whether they be politicians or journalists, sitting on boards such as these.

He prefers people retired from any involvement in politics and I respect that view.

I accepted the offer in good faith and the Minister accepts that I was unwittingly caught up in the process.

Finally, let me thank you personally for the advice and courtesy extended to me since the appointment in August.